In the field of intrusion detection, i.e., the use of devices to detect the presence of physical objects for such uses as anti-burglar interception, and the like, it is known to use devices which are sensitive to infra-red radiation as it is propagated by objects, such as the human or other animal bodies, which are warm, and to cause the output of such detectors to pass through appropriate electronic circuits so that the movement of such a body from one zone of detection into another zone will cause an alarm to be triggered. In this connection, reference is made to U.S. Pat. No. 3,760,399.
However, a problem with prior art devices has been that they require the use of a multiplicity of detectors, as a single large group or as a grouping of smaller groups, in order to effect a wide scanning range without an intolerable amount of distortion. This increases the cost of the units significantly, not only because of the cost of the detectors, but because the units as a whole are larger and more complex. Additionally, prior art devices tended to be suited for single or limited applications in terms of the angular scan they are capable of monitoring, which also tends to increase the cost of units, since this made it impossible to produce larger production lots which can easily be modified for the particular usages desired.
Accordingly, it is an object of the present invention to provide devices for effecting a wide scanning range in intrusion detector devices with a reduced number of detectors. Yet another object of this invention is to provide a detector means that is capable of scanning a wide field without an intolerable amount of distortion. Another object of this invention is to provide such devices in such a form that they are readily adaptable to being modified for any of a number of different applications and scan widths. Still another object of the present invention is to provide a sensor unit with a narrow field of view which can be easily adapted to scan an effectively wide field by adding or substituting various combinations of lenses and/or reflectors. Yet another object of the present invention is to provide such devices in a form which is structurally simple and inexpensive to produce.